Michigan is likely to join 23 other states with right-to-work laws. Republicans passed legislation yesterday through the state's House and Senate amid strong opposition from unions.

Organized labor had long maintained a strong foothold across America's Rust Belt until recently. It was only this past February that Indiana became the first state in over a decade to adopt a new right-to-work law. A similar effort in Ohio wasn't successful.

The idea of such a setback in Michigan, a longtime cradle of organized labor, had seemed next to impossible. So how has this happened? Dale Belman, professor at Michigan State University’s School of Human Resources and Labor Relations, notes that union representation in his state has slipped to 18 percent of workers.

"With the decline in manufacturing, unionization has declined in the Rust Belt, pretty substantially."

The political balance also shifted, with the rise of the Tea Party in legislatures across the region. But Belman believes labor could eventually reclaim some ground:

"Of course, what we're looking at now, in this case, is a lame-duck session, when things are actually starting to shift back," he says.

Belman points out the labor-management alliance between large auto companies and their unions voiced opposition to the change in Michigan -- a sign that labor relations with the carmakers have actually been on the upswing.